Ethical questions for security experts

Alex Stamos's Defcon 21 presentation The White Hat’s Dilemma
is a compelling and fascinating look at the ethical issues associated with information security work in the era of mass surveillance, cyberwar, and high-tech extortion and crime.

It gets especially interesting when it delves into hypotheticals for security experts, like:

You find a critical remote exploit in a very
widespread product. Do you: